The present invention relates to a tuyere for a melting furnace, especially for a blast furnace.
Among tuyeres of this kind known heretofore, there is one disclosed in U.S. Pat. No. 3,826,479, which is devised such that, with a view to not only improving the melting resistance of the tuyere, especially the melting resistance of the fore end portion thereof, but also maintaining a high temperature of the hot blast which is sent therein, the water cooling chamber formed in between the inner and outer walls is divided into an inner water cooling chamber and an outer water cooling chamber by means of an intermediate wall disposed therein, a guide wall is provided in at least the outer water cooling chamber so as to form a helical passage, whereby the cooling water is forcibly introduced into the outer water cooling chamber, led to the inner water cooling chamber thereafter, and then discharged from the inner water cooling chamber.
However, a tuyere of this type has the drawback that a portion such as the upper part of the tuyere is subjected to a relatively high heat load due to molten pig iron, etc. (hereinafter called "high heat load portion") compared with other portions and it is difficult to prevent damage caused by the melting effectively.
In order to eliminate this drawback, therefore, it is conceivable to impart a high velocity to the current of cooling water running through the helical passage. On this occasion, however, the head loss of the cooling water increases almost in proportion to the square of the velocity of the current, and accordingly, in order to increase the velocity of the current throughout the helical passage, the cooling equipment should be a large size which would require bulky equipment and further entail an increase in the cost of operation thereof.